U.S. patent application number 10/886122 was filed with the patent office on 2005-10-06 for laser processing apparatus with polygon mirror.
Invention is credited to Han, You-Hie.
Application Number | 20050218128 10/886122 |
Document ID | / |
Family ID | 34925414 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050218128 |
Kind Code |
A1 |
Han, You-Hie |
October 6, 2005 |
Laser processing apparatus with polygon mirror
Abstract
The disclosure is directed to a laser processing apparatus
employing a polygon mirror, capable of processing an object
efficiently. The apparatus is comprised of a laser generator for
emitting a laser beam, a polygon mirror rotating at the axis and
having a plurality of reflection planes which reflect the laser
beam incident thereon from the laser generator, and a lens
irradiating the laser beam on an object, e.g., a wafer, that is
settled on a stage, after condensing the laser beam reflected from
the polygon mirror. In applying the laser beam to the wafer in
accordance with a rotation of the polygon mirror, the stage on
which the wafer is settled moves to enhance a relative scanning
speed of the laser beam, which enables an efficient cutout
operation for the wafer. As it uses only the laser beam to cutout
the wafer, there is no need to change any additional devices, which
improves a processing speed and cutout efficiency. Further, it is
available to control a cutout width and to prevent a recasting
effect by which vapors generated from the wafer during the cutout
process are deposited on cutout section of the wafer, resulting in
accomplishing a wafer cutout process in highly fine and precise
dimensions.
Inventors: |
Han, You-Hie; (Daejeon-si,
KR) |
Correspondence
Address: |
SHERIDAN ROSS PC
1560 BROADWAY
SUITE 1200
DENVER
CO
80202
|
Family ID: |
34925414 |
Appl. No.: |
10/886122 |
Filed: |
July 6, 2004 |
Current U.S.
Class: |
219/121.74 ;
257/E21.238 |
Current CPC
Class: |
B23K 26/40 20130101;
B23K 26/08 20130101; B23K 26/082 20151001; B23K 26/0736 20130101;
B23K 26/0821 20151001; B23K 2103/50 20180801; B23K 2101/40
20180801; H01L 21/3043 20130101 |
Class at
Publication: |
219/121.74 |
International
Class: |
B23K 026/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2004 |
KR |
10-2004-0022270 |
Claims
What is claimed is:
1. A laser processing apparatus with a polygon mirror for
processing an object by a laser beam, comprising: a laser generator
for emitting the laser beam; a polygon mirror constructed of a
plurality of reflection planes that reflect the laser beam, which
is emitted from the laser generator, thereon while rotating on an
axis; and a lens for condensing the laser beam reflected on the
polygon mirror and irradiating the laser beam on the object.
2. The laser processing apparatus with the polygon mirror according
to claim 1, which further comprises: a polygon mirror driver
rotating the polygon mirror in a constant speed to make the
reflection planes revolve with a predetermined angular velocity; a
stage on which the object is settled; and a stage transfer unit for
transferring the stage toward a predetermined direction.
3. The laser processing apparatus with the polygon mirror according
to claim 2, wherein the stage transfer unit transfers the stage
reverse to a rotating direction of the polygon mirror.
4. The laser processing apparatus with the polygon mirror according
to claim 1, which further comprises a beam transformer for
converting a sectional pattern of the laser beam condensed on the
lens into an ellipse.
5. The laser processing apparatus with the polygon mirror according
to claim 4, wherein the beam transformer converts the laser beam to
be shaped with the sectional pattern as the ellipse whose long
diameter is arranged along a processing direction and then
irradiates the converted laser beam on the object.
6. The laser processing apparatus with the polygon mirror according
to claim 5, wherein a short diameter of the elliptical section of
the laser beam is associated with a processing width by the laser
beam, the width being adjustable by controlling the short
diameter.
7. A laser processing apparatus with a polygon mirror for
processing a wafer, comprising: a laser generator for emitting a
laser beam; a polygon mirror constructed of a plurality of
reflection planes that reflect the laser beam, which is emitted
from the laser generator, thereon while rotating on an axis; and a
lens for condensing the laser beam reflected on the polygon mirror
and irradiating the laser beam on the wafer that is settled on a
stage.
8. The laser processing apparatus according to claim 7, which
further comprises: a polygon mirror driver for rotating the polygon
mirror in a constant speed to make the reflection planes revolve
with a predetermined angular velocity; and a stage transfer unit
for transferring the stage along a predetermined direction.
9. The laser processing apparatus with the polygon mirror according
to claim 8, wherein the stage transfer unit transfers the stage
reverse to a rotating direction of the polygon mirror.
10. The laser processing apparatus with the polygon mirror
according to claim 7, which further comprises a beam transformer
for converting a sectional pattern of the laser beam condensed on
the lens into an ellipse.
11. The laser processing apparatus with the polygon mirror
according to claim 10, wherein the beam transformer converts the
laser beam to be shaped with the sectional pattern as the ellipse
whose long diameter is arranged along a processing direction and
then irradiates the converted laser beam on the wafer.
12. The laser processing apparatus with the polygon mirror
according to claim 11, wherein a short diameter of the elliptical
section of the laser beam is associated with a processing width by
the laser beam, the width being adjustable by controlling the short
diameter.
13. The laser processing apparatus with the polygon mirror
according to claim 10, which further comprises a beam expander for
enlarging a sectional diameter of the laser beam emitted from the
laser generator, the enlarged laser beam being condensed on the
lens after reflected on the polygon mirror and being incident on
the beam transformer.
14. The laser processing apparatus with the polygon mirror
according to claim 7, wherein the lens condenses the laser beam
thereon and then irradiates the laser beam on the wafer in
perpendicular.
15. The laser processing apparatus with the polygon mirror
according to claim 7, wherein a scanning length of the laser beam
applied to the wafer from one of the reflection planes in
accordance with the rotation of the polygon mirror is adjustable by
product of a focal distance of the lens and a scanning angle of the
laser beam reflected from the reflection plane of the polygon
mirror.
16. The laser processing apparatus with the polygon mirror
according to claim 15, wherein the scanning angle of the laser beam
is a reflection angle formed by the beginning and rear parts of the
reflection plane.
17. The laser processing apparatus with the polygon mirror
according to claim 7, wherein the laser beam reflected from the
reflection plane in accordance with the rotation of the polygon
mirror is irradiated on the wafer being overlapped in a
predetermined number and the predetermined number of overlapping is
controllable by adjusting an angular velocity of the polygon mirror
while a transfer velocity of the stage retains constant.
18. The laser processing apparatus with the polygon mirror
according to claim 7, wherein the laser beam reflected from the
reflection plane in accordance with the rotation of the polygon
mirror is irradiated on the wafer being overlapped in a
predetermined number and the predetermined number of overlapping is
controllable by adjusting a transfer velocity of the stage while an
angular velocity of the polygon mirror retains constant.
Description
TECHNICAL FIELD
[0001] The present invention relates to a laser processing
apparatus with a polygon mirror capable of processing an object by
reflecting a laser beam on the polygon mirror.
BACKGROUND ART
[0002] Since apparatuses using a laser beam have more advantage for
cutting silicon wafers than other mechanical apparatuses, various
studies about them have been advanced. One of the most advanced
apparatus for cutting a wafer is an apparatus using a laser beam
guided by ejected water from a high-pressure water jet nozzle.
[0003] A wafer cutout apparatus employing the high-pressure water
jet nozzle irradiates a laser beam on a wafer with ejecting water
through a high-pressure jet nozzle. As the water jet nozzle is
easily worn away due to the high pressure, the nozzle has to be
changed periodically.
[0004] The periodic change of the high-pressure jet nozzle causes
inconveniences in conducting the wafer cutout process. It also
results in lower productivity and higher manufacturing cost.
[0005] Also, since it is difficult for a conventional wafer cutout
apparatus to offer fine line width, there are problems in adopting
the apparatus to high-precision process.
[0006] Meanwhile a wafer cutout process using only a laser beam
brings about a recasting effect which means vapors evaporated by a
laser beam are deposited on cutout sides of wafer. It interrupts a
wafer cutout process.
DISCLOSURE OF INVENTION
[0007] To solve the aforementioned problems, an object of the
present invention is to provide a laser processing apparatus with a
polygon mirror, capable of processing an object such as a wafer
precisely by preventing a recasting effect without changing any
additional devices.
[0008] In the embodiment of the invention, a laser processing
apparatus with a polygon mirror is comprised of: a laser generator
for emitting a laser beam; a polygon mirror constructed of a
plurality of reflection planes that reflect the laser beam which is
emitted from the laser generator, thereon while rotating on an
axis; and a lens for condensing the laser beam which is reflected
on the polygon mirror and irradiating the laser beam on the
object.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A through 1C are schematic diagrams illustrating
conceptual features of a laser processing apparatus employing a
polygon mirror in accordance with the present invention.
[0010] FIG. 2 is a schematic diagram illustrating a conceptual
feature of the laser processing apparatus employing the polygon
mirror in accordance with the present invention.
[0011] FIG. 3 is a diagram illustrating overlapping laser beams in
accordance with the present invention.
[0012] FIG. 4 is a diagram illustrating an exemplary embodiment of
the laser processing apparatus with the polygon mirror in
accordance with the present invention.
[0013] FIG. 5 is a diagram illustrating another embodiment of the
laser processing apparatus with the polygon mirror in accordance
with the present invention.
[0014] FIG. 6 is a flow chart explaining a procedure of processing
an object in accordance with the present invention.
[0015] FIG. 7 is a schematic diagram illustrating a configuration
of wafer processing by the laser processing apparatus with the
polygon mirror in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIGS. 1A through 1C are schematic diagrams illustrating a
conceptual feature of a laser processing apparatus employing a
polygon mirror in accordance with the present invention.
[0017] As shown in FIGS. 1A through 1C, the laser processing
apparatus is comprised of a polygon mirror 10 having a plurality of
reflection planes and rotating at an axis 11, and a telecentric
f-theta lens 20 condensing laser beams reflected from the
reflection planes thereon. The lens 20 is installed in parallel
with a stage 30 on which a wafer 40 to be cut out is settled, in
order to condense laser beams reflected from the reflection planes
thereon. Thus, a laser beam condensed on the lens 20 is irradiated
to the wafer in perpendicular, which enables the wafer 40 (e.g., a
semiconductor wafer) to be processed (able to be cut out) in a
predetermined shape.
[0018] While the lens 20 may be composed of a couple groups of
lenses, this embodiment uses a single lens in convenience on
description.
[0019] FIGS. 1A through 1C illustrate the features that a laser
beam reflected from the reflection plane 12 is applied to the wafer
40 being condensed through the lens 20 while the polygon mirror 10
is rotating in an anti-clockwise direction at the axis 11.
[0020] Referring to FIG. 1A, laser beams are reflected from the
beginning part of the reflection plane 12 in accordance with the
rotation of the polygon mirror 10, and then incident on a left end
of the lens 20. The reflected laser beams are condensed on the lens
20 and irradiated to a predetermined position S1 of the wafer 40 in
perpendicular.
[0021] Referring to FIG. 1B, when the polygon mirror 10 more
advances its rotation to reflect the laser beams on a central part
of the reflection plane 12, the reflected laser beams are incident
on a central position of the lens 20 and condensed on the lens 20.
The condensed laser beam on the lens 20 is irradiated on a
predetermined position S2 of the wafer 40 in perpendicular.
[0022] Referring to FIG. 1C, when the polygon mirror 10 further
advances its rotation, more than the case of FIG. 1B, to reflect
the laser beams on a rear part of the reflection plane 12, the
reflected laser beams on the rear part are incident on a right end
of the lens 20 and condensed on the lens 20. The condensed laser
beam on the lens 20 is irradiated on a predetermined position S3 of
the wafer 40 in perpendicular.
[0023] As aforementioned throughout FIGS. 1A to 1C, the laser beams
are applied to the predetermined positions S1 to S3 on the wafer 40
in accordance with the anti-clockwise rotation of the polygon
mirror 10. The distance from S1 to S3 is regarded to as a scanning
length S.sub.L that means an interval to irradiate the wafer 40 by
the reflection plane 12 along the rotation of the polygon mirror
10. A reflection angle of the laser beam, which is formed by the
beginning and rear parts of the reflection plane 12 is referred to
as a scanning angle .theta..
[0024] Hereinafter, the theoretical feature of the present
invention will be described in more detail.
[0025] FIG. 2 illustrates a schematic configuration of the laser
processing apparatus employing the polygon mirror in accordance
with the present invention.
[0026] Referring to FIG. 2, the polygon mirror 10 constructed with
n-numbered reflection planes rotates in a constant speed at the
axis 11 in an angular velocity of .omega. and a cycle period T. A
laser beam incident thereon is reflected from the reflection plane
12 and irradiated on the wafer 40 through the lens 20.
[0027] In the polygon mirror 10 having the n-numbered reflection
planes 12, the scanning angle .theta. of the laser beam when one of
the reflection planes 12 is rotating is summarized as the following
Equation 1. 1 = 2 ( 2 - 1 ) 1 = + - 2 2 = + - 2 + 2 n = 4 n [
Equation 1 ]
[0028] From the Equation 1, it can be seen that the scanning angle
.theta. is twice the central angle 2 ( 2 n )
[0029] on the reflection plane 12 of the polygon mirror 10.
Therefore, the scanning length S.sub.L, that is a range of
irradiation on the wafer 40 by the reflected laser beam applied
from the reflection plane 12 of the polygon mirror 10, is
determined by a morphological characteristic of the lens 20, as
follows. 3 S L = f .times. = 4 f n S L : Scanning length f : Focal
distance : Scanning angle [ Equation 2 ]
[0030] According to Equation 2, a laser beam reflected from each of
the reflection planes 12 of the polygon mirror 10 while the polygon
mirror 10 is rotating is irradiated on the wafer 40 by the length
of S.sub.L. In other words, the scanning length S.sub.L of a laser
beam irradiated on the wafer 40 in accordance with the rotation of
the polygon mirror 10 is obtained from a product of the focal
length .function. and the scanning angle .theta. of the laser beam
reflected from the reflection plane 12 of the polygon mirror
12.
[0031] By the way, as the polygon mirror 10 has the n-numbered
reflection planes 12, an n-times scanning with the scanning length
S.sub.L is available in every one cycle of rotation of the polygon
mirror 10. That is, a laser beam irradiated on the wafer 40 is
applied to the wafer 40 by the scanning length S.sub.L, overlapping
in the wafer 40 by the number of the reflection planes 12 of the
polygon mirror 10 when the polygon mirror 10 rotates one time. A
scanning frequency during a unit time interval (e.g., one second)
may be obtained from the following Equation 3. 4 Scanning frequency
= n 2 = n T : Angular velocity of the polygon mirror T : Cycle
period of the polygon mirror [ Equation 3 ]
[0032] From Equation 3, in the condition with the n-numbered
reflection planes 12 on the polygon mirror 10, it is possible to
adjust the scanning frequency by controlling the cycle period or
the angular velocity of the polygon mirror 10. In other words, the
scanning length S.sub.L is controllable in desired times of
overlapping by varying the cycle period T or the angular velocity
.omega. of the polygon mirror 10.
[0033] If the angular velocity .omega. of the polygon mirror 10 is
constant, a relative wafer 40 scanning speed of the laser beam
reflected from the polygon mirror 10 is enhanced by transferring
the stage 30, on which the wafer 40 is settled, toward the
direction reverse to the rotating direction of the polygon mirror
10. In other words, when the stage 30 is transferred to the
direction reverse to the rotating direction of the polygon mirror
10, a wafer 40 scanning speed of the laser beam S.sub.L gets faster
compared to the wafer 40 scanning speed of the laser beam when the
stage 30 is standing without moving.
[0034] Such overlaps with the scanning length S.sub.L, as
illustrated in FIG. 3, progress along the direction reverse to the
transfer direction of the stage 30 where the wafer 40 is settled.
As a result, the wafer 40 on the stage 30 is scanned and cut out by
the laser beam along the direction reverse to the transfer
direction of the stage 30. During this, the scanning lengths
S.sub.L continuously overlap from each other in a uniform range, in
which the number of overlapping times may be adjustable by
controlling the transfer speed of the stage 30.
[0035] Provided that a migration distance by the scanning length
S.sub.L is l along the transfer of the stage 30, an overlapping
degree N of the scanning length may be represented in
S.sub.L/l.
[0036] The migration distance l denotes a dimension by which the
stage 30 with velocity v moves for a time until one of the
reflection planes 12 completes to rotate, being summarized in the
following Equation 4. The overlapping degree N is represented in
Equation 5. 5 l = v n T = v T n = 2 v n [ Equation 4 ] Overlapping
degree ( N ) = S L l = 4 f v T = 2 f v [ Equation 5 ]
[0037] By summarizing the aforementioned description, the angular
velocity .omega. of the polygon mirror 10 with the overlapping
degree N while the wafer 40 is cutting out in the velocity v
results in Equation 6 as follows. 6 = N v 2 f [ Equation 6 ]
[0038] As represented in Equation 6, the angular velocity is
obtained by dividing a product of the overlapping degree N of the
laser beam and the cutout velocity v with a double value of the
focal length .function. of the lens 20, where the cutout velocity v
corresponds to the transfer speed of the stage 30 settling the
wafer 40 thereon.
[0039] While this embodiment uses a polygon mirror shaped with
eight reflection planes (i.e., n=8) in eight corners, other
polygonal patterns may be available in modification under the scope
of the present invention.
[0040] FIG. 4 illustrates an exemplary embodiment of the laser
processing apparatus with the polygon mirror in accordance with the
present invention.
[0041] Referring to FIG. 4, the laser processing apparatus with the
polygon mirror according to the present invention is comprised of a
controller 110 for conducting an overall operation, an input unit
120 for entering control parameters and control commands, a polygon
mirror driver 130 for actuating the polygon mirror 10, a laser
generator 140 for emitting laser beams, a stage transfer unit 150
for transferring the stage 30, on which the wafer 40 is settled, in
a predetermined direction, a display unit 160 for informing the
external users of current operating states, and a storage unit 170
for storing data relevant thereto.
[0042] The polygon mirror driver 130 includes a plurality of the
reflection plane 12, being configured to make the polygon mirror
10, which has multiple planes, rotate in a predetermined velocity
at the axis 11. The polygon mirror 10 uniformly rotates at the axis
11 in the predetermined velocity by means of a motor (not shown)
under control of the controller 110.
[0043] The laser generator 140 is configured to emit the laser
beams to process the wafer 40 as an object settled on the stage 30,
generating ultraviolet-ray laser beams under control of the
controller 110 in this embodiment.
[0044] The stage transfer unit 150 is configured to transfer the
stage 30, on which the wafer 40 as an object to be treated is
settled, in a predetermined velocity.
[0045] In the structure of the laser processing apparatus, laser
beams emitted from the laser generator 140 are incident on the
polygon mirror 10 under control of the controller 110. The laser
beams applied to the polygon mirror 10 are reflected toward the
lens 20 from the reflection planes 12, which are rotating by the
polygon mirror driver 130, within the range of the scanning angle
.theta.. The laser beams reflected from the reflection planes 12
are condensed on the lens 20, and the condensed laser beam is
irradiated on the wafer 40 in perpendicular.
[0046] The laser beam being irradiated on the wafer 40 while one of
the reflection planes 12 of the polygon mirror 10 is rotating
migrates by the scanning length S.sub.L along the direction reverse
to the transfer direction of the stage 30.
[0047] FIG. 5 illustrates another embodiment of the laser
processing apparatus with the polygon mirror in accordance with the
present invention.
[0048] Referring to FIG. 5, the laser processing apparatus with the
polygon mirror, in accordance with another embodiment of the
present invention, is basically comprised of a controller 110 for
conducting an overall operation, an input unit 120 for entering
control parameters and control commands, a polygon mirror driver
130 for actuating the polygon mirror 10, a laser generator 140 for
emitting laser beams, a stage transfer unit 150 for transferring
the stage 30, on which the wafer 40 is settled, in a predetermined
direction, a display unit 160 for informing the external users of
current operating states, and a storage unit 170 for storing data
relevant thereto.
[0049] These structures of FIG. 5 are as same as those of FIG. 4.
But, the laser processing apparatus with the polygon mirror in FIG.
5 is further comprised of a beam expander 210 for enlarging
diameters of pointing laser beams emitted from the laser generator
140 and then applying the enlarged laser beams to the polygon
mirror 10, and a beam transformer 220 for converting the laser
beam, which is condensed on the lens 20 after being reflected from
the polygon mirror 10, into an elliptical pattern. At this time the
beam transformer 220 may be easily implemented by employing a
cylindrical lens.
[0050] The enlarged laser beams incident on the polygon mirror 10
are reflected toward the lens 20 on the reflection planes 12 of the
polygon mirror 10 within the range of the scanning angle .theta..
The laser beam reflected from the reflection planes 12 is condensed
on the lens 20, converted into an elliptical pattern by the beam
transformer 220 in sectional view, and then irradiated on the wafer
40 in perpendicular.
[0051] As the irradiated laser beam has elliptical sectional
pattern, a long diameter of the elliptical section corresponds to a
direction of cutout processing while a short diameter of the
elliptical section corresponds to a width of cutout processing.
[0052] When one of the reflection planes 12 is rotating on the axis
11, the laser beam irradiated on the wafer 40 is shifted as the
scanning length S.sub.L along the direction reverse to the transfer
direction of the stage 30.
[0053] Hereinafter, it will be described in detail about a
procedure of processing an object (i.e., the wafer 40) by means of
the laser processing apparatus with the polygon mirror shown in
FIG. 5.
[0054] FIG. 6 is a flow chart explaining a procedure of processing
an object, in accordance with the present invention.
[0055] Referring to FIG. 6, in order to process the wafer, i.e., to
cut the wafer 40 out, first control parameters for a rotation
velocity of the polygon mirror 10 and a transfer velocity of the
stage 30 in the input unit 120 are established, in accordance with
a type of the wafer 40 to be processed (step S10). Such setting
operations may be simply carried out by retrieving information
menus from the storage unit 170 after registering the information,
that has been preliminarily designed for wafer types and processing
options (e.g., cutting, grooving, and so on), in the storage unit
170.
[0056] After completing the establishment for the control
parameters, the controller 110 enables the polygon mirror driver
130 to rotate the polygon mirror 10 in a rotation velocity that has
been predetermined at the step S10 (step S20), and also enables the
stage transfer unit 150 to transfer the stage 30 in a predetermined
velocity (step S30). At this point the controller 110 makes the
laser generator 140 emit the laser beam (step S40).
[0057] Then, the laser beam emitted from the laser generator 140 is
incident on the polygon mirror 10 with being enlarged in its
sectional diameter after passing through the beam expander 210. The
laser beam incident on the polygon mirror 10 is reflected from the
reflection plane 12 of the polygon mirror 10 rotating at the axis
11, toward the lens 20 within the range of the scanning angle
.theta..
[0058] The lens 20 condenses the laser beam reflected from the
polygon mirror 10, and the condensed laser beam on the lens 20 is
irradiated on the wafer 40 in perpendicular after being converted
into an elliptical pattern in sectional view by the beam
transformer 220. The laser beam finally applied to the wafer 40 has
a elliptical sectional pattern in which the long diameter accords
to the cutout direction of the wafer 40, i.e., a progressing
direction of processing, which extends an irradiation range of the
laser beam over the wafer 40 a time, while the short diameter
corresponds to a cutout thickness, i.e., a cutout width of
processing.
[0059] During the procedure, as the polygon mirror 10 rotates with
a constant speed, a plurality of the laser beam irradiated on the
wafer 40 are overlapped in predetermined times by a plurality of
the scanning length S.sub.L over the wafer 40.
[0060] In addition, as the stage 30 settling the wafer 40 thereon
is transferred in the direction reverse to the rotation direction
of the polygon mirror 10, a relative speed of irradiation with the
scanning length by the laser beam on the wafer 40 becomes faster
which makes the wafer cutout process efficient (step S50).
[0061] On the other hand, the laser beam emitted from the laser
generator 140 is directly irradiated on the wafer 40 when it skips
the steps of the beam expander 210 and the beam transformer
220.
[0062] FIG. 7 illustrates a configuration of processing the wafer
40 by the laser processing apparatus with the polygon mirror in
accordance with the present invention.
[0063] As aforementioned, the laser beam enlarged with its
sectional diameter after passing through the beam expander 210 is
incident on the polygon mirror 10. The laser beam incident on the
polygon mirror 10 is reflected within the range of the scanning
angle .theta. toward the lens 20 on the reflection plane 12 of the
polygon mirror 10 that is rotating. The lens 20 condenses the laser
beam. The laser beam condensed on the lens 20 is shaped into a
sectional elliptical pattern by the beam transformer 220 and then
irradiated on the wafer 40.
[0064] During this, as the laser beam irradiated on the wafer 40
has the sectional elliptical pattern, the long diameter of the
ellipse is associated with a progressing direction on the wafer 40
by the laser beam while the short diameter of the ellipse is
associated with a cutout width on the wafer 40 by the laser
beam.
[0065] As illustrated in FIG. 7, the elliptical laser beam
irradiated on the wafer 40 is progressing along the direction of
its long diameter, accompanying with the cutout width by its short
diameter. In other words, the cutout width 41 of the wafer 40 is
adjustable by controlling the short diameter of the elliptical
section of the laser beam, which is established by the beam
transformer 220.
[0066] During the irradiation on the wafer 40 by the laser beam,
evaporation may be occurred at places on which the laser beam is
irradiated. However, the progressing direction of the laser beam is
reverse to the transfer direction of the wafer 40, as
aforementioned, so that the relative scanning speed of the laser
beam becomes faster and the long diameter of the laser beam is
arranged to the processing direction (i.e., the cutout direction).
As a result, a cutout section 42 has a slope throughout the cutout
process, by which vapors escaping from the wafer material due to
the irradiation of the laser beam are easily discharged without
depositing on the cutout plane 42 during the process.
[0067] Moreover, since the rapid overlapping with the laser beam
along the processing direction makes the cutout portion of the
wafer 40 be swiftly evaporated, the wafer processing is carried out
easily without such as a recasting effect for which vapors from the
wafer material are deposited on the cutout wall 43 of the wafer
40.
[0068] Although the aforementioned, embodiments is exemplarily
describes as being applicable to processing a semiconductor wafer,
the present invention is also available to processing other
substrates or boards such as plastics, metals, and so on.
[0069] As described above, the laser processing apparatus with the
polygon mirror in accordance with the present invention needs not
any change of additional devices because a laser beam is enough to
perform the cutout process, which enables the process to be rapidly
carried out in easy and efficiency. Furthermore, since the present
invention provides an efficient technique to able to control the
cutout width by adjusting the short diameter of the elliptical
laser beam and to prevent a recasting effect that causes vapors
escaping from an object to be cut out, it is advantageous to
processing a wafer in highly precise operations, as well as normal
objects.
[0070] Although the present invention has been described in
connection with the embodiment of the present invention illustrated
in the accompanying drawings, it is not limited thereto. It will be
apparent to those skilled in the art that various substitution,
modifications and changes may be thereto without departing from the
scope and spirit of the invention.
* * * * *